Magnetic cores for electrical inductrion apparatus and the method of producing same



Nov.27, 1956 c. G. DUENKE 2,771,664

MAGNETIC CORES FOR ELECTRICAL INDUCTION APPARATUS AND THE METHOD OFPRODUCING SAME Filed March 14, 1952 FIG 4 & 20

INVENTOR.

CLARENCE G, DUENM:

BY 4 z; w 11 z; FIG. 7. 4

United States Patent 6 MAGNETIC CORES FOR ELECTRICAL INDUC- TIONAPPARATUS AND THE METHOD OF PRODUCING SAME Clarence G. Duenke, WebsterGroves, Mo., assignor to Moloney Electric Company, St. Louis, Mo., acorporation of Delaware Application March 14, 1952, Serial No. 276,618

4 Claims. (Cl. 29155.57)

In producing magnetic cores of the continuous, tape wound constructionit has been necessary heretofore to use forms or internal formers ofsome type to preserve the shapes of the cores during various steps inthe processing thereof, such, for instance, as strain annealing,bonding, etc., and the present invention has for its predominant objectthe provision of a method which eliminates the need for costly formerswith a resultant substantial saving in cost of production and in labor,and the elimination of the cost of heating the added weight of theformers during portions of the manufacturing process which would involveheating.

Fig. 1 is a side elevation of a core construction in accordance withthis invention.

Fig. 2 is a perspective view of a form employed in producing a core inaccordance with this invention.

Fig. 3 is a schematic view showing an early stage of the core windingoperation when the form shown in Fig. 2 is employed.

Fig. 4 is a fragmentary perspective view illustrating a form employedfor producing a core in accordance with a modified form of theinvention.

Fig. 5 is a schematic view illustrating an early stage of the winding ofa core with the aid of the form shown in Fig. 4.

Fig. 6 illustrates still another type of form for producing a corehaving three stiffening structures in the window thereof.

Fig. 7 is a schematic view illustrating an early stage of the winding ofa core with the aid of the form shown in Fig. 6.

In the drawing, wherein are shown for purposes of illustration, merely,several embodiments of the invention, A designates in Fig. 1 a magneticcore loop made in accordance with this invention. The core loop A is ofthe continuous, tape wound construction and it is characterized by beingprovided with a box-like rectangular stiffening element or structure 1located within the window 2 of the core which is formed from the leadingend of the magnetic tape material of which the core is formed. Byreferring to Fig. 1 it will be noted that the box-like stiffeningstructure 1 comprises a short leg portion 3 from which is extended a legportion 4 that extends from one side of the window 2 of the core loop Ato the opposite side thereof. The leg portion 4 merges into a legportion 5 which parallels the short leg portion 3 at the opposite sideof the core window, and said leg portion 5 merges into a leg portion 6that parallels the leg portion 4. From the leg portion 6 the magnetictape material of which the core loop A is formed is extended to producein a continuous manner the core loop, the outer free end portion of thetape material being temporarily held in place by a short length ofsuitable adhesive tape 7. By providing a core loop with a stiffeningstructure within the window thereof, as described above, the core loopis supplied with sufficient rigidity to withstand the handling to whichit is subjected during processing thereof without the use of costlyformers for supplying the required rigidity.

ice

In producing core loops in accordance with this invention a core windingmachine (not shown) is employed and this machine is provided with a form8, such as that shOWn in Fig. 2. The form 8 of Fig. 2 comprises a bodyportion 9 in which is formed a pair of parallel slots 10, these slotsbeing open at the forward end of the body portion 9 of the form 8 andbeing closed at their rear ends, and said slots provide the form with apair of forwardly extended arms or form portions 11, and an intermediateor central, forwardly extended arm or form portion 12 which is disposedbetween said form portions 11. By referring to Figs. 2 and 3 it will benoted that the intermediate form portion 12 of the form 8 is recessed ordepressed at its top and bottom faces, as is indicated at 13, this beingfor a purpose to be hereinafter set forth. The form 8 is provided alsowith a spindle 14 which is arranged in cooperation with a part of thecore winding machine with which the form 8 is associated for corewinding operations so as to cause the form to be rotated by the corewinding machine.

In producing a core loop in accordance with this invention an endportion of the tape from which the core loop is to be formed is bentrelative to the adjacent part of said tape and is disposed in either ofthe recesses or depressions 13 of the intermediate portion 12 of theform 8, this bent portion being the tape portion 3 shown in Figs. 1 and3. The portions 4, 5, and 6 of the box-like structure 1 are thenarranged in place by hand, the portions 4 and 6 being disposed in theslots 10 of the form, and the portion 5 being extended across the faceof the intermediate form portion 12 opposed to the face thereof withwhich the tape portion 3 contacts. When the leading portion of the tapehas been arranged with respect to the form 8 as shown in Fig. 3, thecore winding machine is set in motion and the form 8 is rotated. Thusthe tape is drawn from a reel (not shown) and is wound on the rotatingform to produce the core loop A shown in Fig. 1, the free end of thetape being secured in place by the strip of adhesive tape previouslymentioned herein.

From the foregoing it is plain that a core loop provided within itswindow with a stiffening structure, such as that designated by thereference character 1 in Fig. 1, is braced so that it is able towithstand the handling and processing to which the core loop issubjected during production thereof. It is to be understood that thestiffening structure 1 of the core loop A is not a permanent part of thefinished core, but, instead, this stifiening structure serves itsfunction only during the processing of the core, after which saidstiffening structure is stripped out of the core window and is disposedof.

The modified form of the invention illustrated by Figs. 4 and 5contemplates the use in winding a core loop of a form structurewhich'includes a fixed form member or portion 17 and a pair of slidableform members or portions 13, the fixed form portion 17 having aninclined groove 19 formed therein. In producing a core loop with the aidof the form illustrated by Figs. 4 and 5, the form portions 18 areretracted and a bent end portion 20 of the magnetic tape material fromwhich a core loop is being formed is inserted into the inclined groove19 of the fixed form portion 17. The form is then subjected to rotationand the tape of material is wound about the form portion 17 for one ortwo turns to produce a stiffening structure 21, the form portions '18being then moved forwardly of the fixed form portion 17 and the coreloop being wound about the three form portions to the desired number ofturns to produce a core loop having a stiffening structure in the windowthereof.

In accordance with the modified form of the invention illustrated byFigs. 6 and 7, a form structure 22 is employed which comprises a portion23 having three pro- 3 jected form portions 23a, 23b, and 230, thesethree form portions being produced by providing the form portion 23 witha pair of slots 24. As is shown in Fig. 7 the form portions 23a, 23b,and 230 are of less height than the formportions .25, said form portions25 being slidable relative to the form portion 23. In producing a coreloop with the aid. of the form illustrated by Figs. 6 and 7, a bent endportion 26 of the magnetic tape material from which a core loop is beingformed is disposed in contact with a face of the form portion 23a. Themagnetic tape material is then extended through one of the slots 24 andalong a face of the form portion 31), the tape then being extendedthrough the other slot 24. At this time the form portions 25 areretracted and the magnetic tape material extends from said other slotand about the form portions 23a and 23b and finaiiy is extended aboutthe form portion 230. The siidable form portions are then movedforwardly with respect. to the form portions 23a, 23b, and 23c and thetape of magnetic material is wound about the entire form structure so asto produce a core loop having the desired number of turns. From theforegoing it is plain that a core loop is finally produced which isprovided in the window thereof with three box-like stiffeningstructures, these stiffening structures being designated in Fig. 7 bythe reference characters 27, 28, and 29.

I claim:

1. The method of producing a magnetic core loop from magnetic tapecomprising forming the leading end of said tape into a rectangularstiffening element, Winding the tape as a coil around a core form havinga recess in which said stiffening element is disposed, securing thetrailing end of said tape to the outside of said coil, separating saidcore form from said coil thereby forming a central window of said coilin which said stiffening element is disposed, one pair of oppositelyfacing surfaces of said stiffening element bracing opposite interiorsurfaces of the coil with sufficient rigidity to withstand the effectsof forces produced incident to processing said coil, the remaining pairof stiffening element surfaces being spaced from the other interiorsurfaces of said coil, heat treating said coil and the integralstiffening element assembly at annealing temperatures, and removing thestiffening element from said coil window.

2. The method of producing a magnetic core loop from magnetic tapecomprising winding the leading end of said tape around a central arm ofa three-armed rectangular core form, then winding the tape as a coilaround said core form, securing the trailing end of said tape to theoutside of said coil, separating said core form from said coil therebyforming a central Window of said coil in which said stiffening elementis disposed, one pair of oppositely facing surfaces of said stiffeningelement bracing opposite interior surfaces of the coil with sufficientrigidity to withstand the effects of forces produced incident toprocessing said coil, the remaining pair of stiffening element surfacesbeing spaced from the other interior surfaces of said coil, heattreating said coil and the integral stiffening element assembly atannealing temperatures, and removing the stiffening element from saidcoil window.

3. The method of producing a magnetic core loop from magnetic tapecomprising winding several turns of the leading end of said tape arounda first rectangular core form member to produce a rectangular stiffeningelement, positioning additional rectangular core form members atopposite sides of said element as Wound on said first core form member,then winding the tape as a coil around the assembled core form membersand stiffening element, securing the trailing end of said tape to tieoutside of said coil, separating all of said core form members from saidcoil thereby forming a central window of said. coil in which saidstiffening element is disposed, one pair of oppositely facing surfacesof said stiffening element bracing opposite interior surfaces of thecoil with sufiicient rigidity to withstand the effects of forcesproduced incident to processing said coil, the remaining pair ofstiffening element surfaces being spaced from the other interiorsurfaces of said core loop, heat treating said coil and the integralstiffening element assembly at annealing temperatures, and removing thestiffening element from said coil window.

4. The method of producing a magnetic core loop from magnetic tapecomprising passing the leading end of said tape through a slot in arectangular core form member having at least one slot therein, windingthe tape on the form to produce a rectangular stiffening element,positioning additional rectangular core form members on opposite sidesof said element as Wound on said first core form member, then windingthe tape as a coil around the assembled core form members and stiffeningelement, securing the trailing end of said tape to the outside of saidcoil, separating all of said core form members from said coil therebyforming a central window of said coil in which said stiffening elementis disposed, one pair of oppositely facing surfaces of said stiffeningelement bracing opposite interior surfaces of the coil with sufficientrigidity to withstand the effects of forces produced incident toprocessing said coil, the remaining pair of stiffening element surfacesbeing spaced from the other interior surfaces of said core loop, heattreating said coil and the integral stiffening element assembly atannealing temperatures, and removing the stiffening element from saidcoil window.

References Cited in the file of this patent UNITED STATES PATENTS443,256 Logan Dec. 23, 1890 2,313,306 Wiegand Mar. 9, 1943 2,416,989Gauthier Mar. 4, 1947 2,613,430 Sefton et al. Oct. 14, 1952 2,657,456Moody Nov. 3, 1953

